Context Navigation

-              r0d0a212
+              r483838e
     <title>Introduction</title>
+    <para>Boot loading can be a complex area, so a few cautionary
+    words are in order. Be familiar with the current boot loader and any other
+    operating systems present on the hard drive(s) that need to be
+    bootable. Make sure that an emergency boot disk is ready to
+    <warning><para>Configuring GRUB incorrectly can render your system
+    inoperable without an alternate boot device such as a CD-ROM.  This
+    section is not required to boot your LFS system.  You may just
+    want to modify your current boot loader, e.g. Grub-Legacy, GRUB2, or
+    LILO.</para></warning>
+    <para> Ensure that an emergency boot disk is ready to
     <quote>rescue</quote> the computer if the computer becomes
+    unusable (un-bootable).</para>
+    unusable (un-bootable).  If you do not already have a boot device,
+    you can create one.  In order for the procedure below to work,
+    you need to jump ahead to BLFS and install <ulink
+    url="http://www.linuxfromscratch.org/blfs/view/svn/multimedia/xorriso.html">
+    xorriso</ulink>.</para>
+    <para>The procedure involves writing some special GRUB files to specific
+    locations on the hard drive. We highly recommend creating a GRUB boot
+    floppy diskette as a backup. Insert a blank floppy diskette and run the
+    following commands:</para>
+<screen role="nodump"><userinput>cd /tmp &amp;&amp;
+grub-mkrescue --output=grub-img.iso &amp;&amp;
+xorriso -as cdrecord -v dev=/dev/cdrw blank=as_needed grub-img.iso</userinput></screen>
+<screen role="nodump"><userinput>cd /tmp
+grub-mkrescue --output=grub-img.iso
+dd if=grub-img.iso of=/dev/fd0 bs=1440 count=1</userinput></screen>
+  </sect2>
+    <para>Alternatively, a boot CD can be created by using your host system's
+    CD burning tools to burn the <filename>grub-img.iso</filename> on to a
+    blank CD.</para>
+  <sect2>
+    <title>GRUB Naming Conventions</title>
     <para>GRUB uses its own naming structure for drives and partitions in
 …
 cat device.map</userinput></screen>
+  </sect2>
+  <sect2>
+    <title>Setting Up the Configuration</title>
+    <para>GRUB works by writing data to the first physical track of the
+    hard disk.  This area is not part of any file system.  The programs
+    there access GRUB modules in the boot partition.  The default location
+    is /boot/grub/.</para>
     <para>The location of the boot partition is a choice of the user that
     affects the configuration.  One recommendation is to have a separate small
 …
     <para>Using the current lfs partition will also work, but configuration
     for multiple systems is more difficult.</para>
-  </sect2>
-  <sect2>
-    <title>Setting Up the Configuration</title>
     <para>Using the above information, determine the appropriate
 …
     <para>Install the GRUB files into <filename
+    class="directory">/boot/grub</filename>:</para>
+<screen role="nodump"><userinput>grub-install --grub-setup=/bin/true /dev/sda</userinput></screen>
+    <para>We use --grub-setup=/bin/true for now to prevent updating the
+    Master Boot Record (MBR).  In this way, we can test our installation
+    before committing to a change that is hard to revert.</para>
+    <para>Generate <filename>/boot/grub/grub.cfg</filename>:</para>
+<screen role="nodump"><userinput>grub-mkconfig -o /boot/grub/grub.cfg</userinput></screen>
+    <para>Here <command>grub-mkconfig</command> uses the files in <filename
+    class="directory">/etc/grub.d/</filename> to determine the contents
+    of this file. The configuration file will look something like:</para>
+<screen><computeroutput>#
+# DO NOT EDIT THIS FILE
+#
+# It is automatically generated by /usr/sbin/grub-mkconfig using templates
+# from /etc/grub.d and settings from /etc/default/grub
+#
+### BEGIN /etc/grub.d/00_header ###
+set default=0
+set timeout=5
+### END /etc/grub.d/00_header ###
+### BEGIN /etc/grub.d/10_linux ###
+menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" {
+        insmod ext2
+        set root=(hd0,2)
+        search --no-floppy --fs-uuid --set 915852a7-859e-45a6-9ff0-d3ebfdb5cea2
+        linux   /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro
+}
+menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" (recovery mode)" {
+        insmod ext2
+        set root=(hd0,2)
+        search --no-floppy --fs-uuid --set 915852a7-859e-45a6-9ff0-d3ebfdb5cea2
+        linux   /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro single
+}
+menuentry "GNU/Linux, Linux 2.6.28-11-server" {
+        insmod ext2
+        set root=(hd0,2)
+        search --no-floppy --fs-uuid --set 6b4c0339-5501-4a85-8351-e398e5252be8
+        linux   /boot/vmlinuz-2.6.28-11-server root=UUID=6b4c0339-5501-4a85-8351-e398e5252be8 ro
+        initrd  /boot/initrd.img-2.6.28-11-server
+}
+menuentry "GNU/Linux, Linux 2.6.28-11-server (recovery mode)" {
+        insmod ext2
+        set root=(hd0,2)
+        search --no-floppy --fs-uuid --set 6b4c0339-5501-4a85-8351-e398e5252be8
+        linux   /boot/vmlinuz-2.6.28-11-server root=UUID=6b4c0339-5501-4a85-8351-e398e5252be8 ro single
+        initrd  /boot/initrd.img-2.6.28-11-server
+}
+### END /etc/grub.d/10_linux ###
+### BEGIN /etc/grub.d/30_os-prober ###
+### END /etc/grub.d/30_os-prober ###
+### BEGIN /etc/grub.d/40_custom ###
+# This file provides an easy way to add custom menu entries.  Simply type the
+# menu entries you want to add after this comment.  Be careful not to change
+# the 'exec tail' line above.
+### END /etc/grub.d/40_custom ###
+</computeroutput></screen>
+  <note>
+  <itemizedlist>
+      <listitem><para>Even though there is a warning not to edit the file, you
+      can do so as long as you do not re-run
+      <command>grub-mkconfig</command>.</para></listitem>
+      <listitem><para>The <emphasis>search</emphasis> lines are generally not
+      useful for LFS systems as that command only sets an internal GRUB
+      variable used to find the kernel image.  The <emphasis>set root</emphasis>
+      command provides the same capability without the overhead of
+      searching.</para></listitem>
+      <listitem><para>The <emphasis>set root</emphasis> and
+      <emphasis>insmod ext2</emphasis> commands can be moved out of the
+      <emphasis>menuentry</emphasis> sections to apply to all sections of the file.
+      This leads to a simple section like:</para></listitem>
+      </itemizedlist>
+<screen><computeroutput>menuentry "Linux &linux-version;-lfs-&version;" {
+linux   /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro
+}
+</computeroutput></screen>
+  <itemizedlist>
+      <listitem><para>Passing a UUID to the kernel requires an initial ram disk
+      (initrd) not built by LFS.</para></listitem>
+      <listitem><para>If the <filename>/boot</filename> partition is installed
+      on a separate partition, the linux and initrd lines should not have the
+      string <emphasis>/boot</emphasis> prefixed to the file
+      names.</para></listitem>
+      <listitem><para>In this example the kernel files for a Ubuntu
+      installation are also found in <filename
+      class="directory">/boot</filename>.</para></listitem>
+   </itemizedlist>
+   </note>
+  </sect2>
+  <sect2>
+     <title>Testing the Configuration</title>
+     <para>The core image of GRUB is also a Multiboot kernel, so if you already
+     have <emphasis>GRUB Legacy</emphasis> loaded you can load
+     GRUB-&grub-version; through your old boot loader.  To accomplish this, you
+     will need to exit the <command>chroot</command> environment now and
+     re-enter it in the next section to finish the few remaining portions of
+     the book.</para>
+<screen role="nodump"><userinput>/sbin/reboot
+...
+grub> root (hd0,1)
+grub> kernel /boot/grub/core.img
+grub> boot</userinput></screen>
+     <para>Note that the GRUB commands above are assumed to be GRUB Legacy.
+     At this point the GRUB prompt will appear (very similar to GRUB Legacy) and
+     you can explore the interface or boot to one of the systems in the grub.cfg
+     file.</para>
+   </sect2>
+  <sect2>
+     <title>Updating the Master Boot Record</title>
+     <para>If you tested the GRUB configuration as specified above, re-enter
+     the <command>chroot</command> environment.</para>
+    class="directory">/boot/grub</filename> and set up the boot track:</para>
     <warning>
 …
     </warning>
     <para>Update the MBR with:</para>
+<screen role="nodump"><userinput>grub-install /dev/sda</userinput></screen>
+<screen role="nodump"><userinput>grub-setup '&lt;DEVICE&gt;'</userinput></screen>
+    <note><para><application>grub-install</application> is a script and calls another
+    program, grub-probe, that may fail with a message "cannot stat `/dev/root'".
+    If so, create a temporary symbolic link from your root partition to /dev/root:</para>
+    <para>Change the DEVICE above to your boot disk, normally '(hd0)' or /dev/sda.
+    If using (hd0) be sure to escape the parentheses with backslashes or single
+    quotes to prevent the shell from interpreting them as a sub-shell.</para>
+<screen role="nodump"><userinput>ln -sv /dev/sda2 /dev/root</userinput></screen>
+    <para>This program uses the following defaults and are correct if you did not
+    deviate from the instructions above:</para>
+    <para>The symbolic link will only be present until the system is rebooted.
+    The link is only needed for the installation procedure.
+    </para></note>
+    <itemizedlist>
+      <listitem><para>boot image  - boot.img  </para></listitem>
+      <listitem><para>core image  - core.img  </para></listitem>
+      <listitem><para>directory   - /boot/grub</para></listitem>
+      <listitem><para>device map  - device.map</para></listitem>
+      <listitem><para>default root setting - guessed</para></listitem>
+    </itemizedlist>
+  </sect2>
+   <note><para>The root setting is the default value if a 'set root'
+   instruction is not found in grub.cfg.  This is the partition that is
+   searched for the kernel and other supporting files.  It is different from
+   the 'root=' parameter on the 'linux' line in the configuration line.  The
+   latter is the partition the kernel mounts as '/'.  In the example grub.cfg
+   above, both values point to /dev/sda2, but if there is a separate boot
+   partition, they will be different.</para></note>
+  <sect2>
+    <title>Creating the Configuration File</title>
+    <para>Generate <filename>/boot/grub/grub.cfg</filename>:</para>
+    <screen><userinput>cat &gt; /boot/grub/grub.cfg &lt;&lt; "EOF"
+<literal># Begin /boot/grub/grub.cfg
+set default=0
+set timeout=5
+insmod ext2
+set root=(hd0,2)
+menuentry "GNU/Linux, Linux &linux-version;-lfs-&version;" {
+        linux   /boot/vmlinux-&linux-version;-lfs-&version; root=/dev/sda2 ro
+}</literal>
+EOF</userinput></screen>
+    <para>GRUB is an extremely powerful program and it provides a tremendous
+    number of options for booting from a wide variety of devices, operating
+    systems, and partition types.  There are also many options for customization
+    such as graphical splash screens, playing sounds, mouse input, etc.  The
+    details of these options are beyond the scope of this introduction.</para>
+    <note><para>There is a command, <application>grub-mkconfig</application> that
+    can write a configuration file automatically.  It uses a set of scripts in
+    /etc/grub.d/ and will destroy any customizations that you make.  These scripts
+    are designed primarily for non-source distributions and are not recommended for
+    LFS.  If you install a commercial Linux distribution, there is a good chance
+    that this program will be run.  Be sure to back up your grub.cfg file.</para></note>
    </sect2>

Note: See TracChangeset for help on using the changeset viewer.

Context Navigation

Changeset 483838e for chapter08

Legend:

chapter08/grub.xml

Download in other formats: